Yes tubby linton is correct.
Even partially pulled out can lead to parking brake on.This leads to all other braking being disconnected!!!This may not be obvious to the crew until loss of braking is evident.
The braking system is not one of the better systems on airbus aircraft!
Why would you want to be towed to stand if you are on alternate brakes?
Cause we didn't know what actually happened. HYD normal no warnings etc.
@dreamland
Can't realy tell what the problem was cause many parts have been changed thereafter e.g. automatic selector valve, BSCU, parking brake mechanism(!!!)